Social games according to related art include a known video game wherein players battle with each other by using a concept of “deck” (“Sengoku Royale,” [online], Apr. 20, 2010, DeNA Co., Ltd., [Searched on May 29, 2012], the Internet, <URL:http://sngk.mbga.jp/_sngk_top>). A deck is a game contents group composed of a plurality of game contents (such as character cards) selected from game contents owned by a player, and the game contents group is used by the player. The strength of a deck is determined based on, for example, characteristic values (e.g., offensive power and defensive power) assigned to each game content constituting the deck and combination of game contents constituting the deck (e.g., compatibility and special abilities produced by the combination). Additionally, teams each including a plurality of players can battle with each other (team battle).
However, a team battle in the above related art is basically performed individually between each player representing one team and each player representing the other team by using their own decks. The outcome of the entire team battle is determined in accordance with the numbers of wins and losses of the one-to-one battles. Accordingly, the outcome of such team battle is monotonously determined, and the players are unlikely to be continuously attracted.